Circuit arrangement and method for writing magnetic information



. Owl I N. J. ALBANES CIRCUIT ARRANGEMENT AND METHOD FO'R y WRITING MAGNETIC INFORMATION.

Filed NOV. 15,`l955 April 2, 1957 United States Patent O CIRCUIT ARRANGEMENT AND METHOD FOR WRITING MAGNETIC INFORMATION Nicholas J. Albumes, Poughkeepsie, N. Y., assiguor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application November 13, 1953, Serial No. 391,937

lil Claims.V (Cl. 346-74) This invention relates to circuital arrangements and methods for addressing a magnetic surface, for example, on a drum for writing or recording information in the form of magnetic spots on the surface by the delivery of electrical writing energy currents in the form of pulses to write coil sections of a plurality of magnetic writing heads which latter are arranged relative to the magnetic surface to deliver magnetic spot writing flux pulses to it.

ln addressing magnetic drums as hereinbefore mentioned, groups each comprising a plurality of magnetic writing heads are arranged to respectively overlie separate areas of a magnetic surface. Each group of magnetic writing heads is intended to write magnetic information on the area underlying it in response to instructions received from a specified channel source` of signals. The magnetic writing heads in each group make independent magnetic writings, for example, in the form of magnetic spots on the magnetic surface. In other words, each writing head in a group is intended to record a fragment or bit of informationk as instructed by signals received from a specific channel. In the instant application, any magnetic spot written on the magnetic surface by a Writing head is intended to be a record on the surfacey of a trst or a second type of magnetically written information. The first type of magnetically written spot in this invention is a so-called write spot. The second type of magnetically written spot in this invention is a so-called write l spot'. The writingV instructions received by each writing head thus must be energizing currents that will provide a write O magnetic` writing ilux or a write "l magnetic writing flux to the specific writing head.

in the past the write 0 writing flux and the-write l writing ux for each writing head of a channel group has been supplied by use of electron discharge means such as triode vacuum tubes, one set of such tubes being utilized to provide the necessary write 0 instructing current for each writing head and another set of such tubes being utilized to provide the write l instructing current for each writing head. This has required the use of large numbers* of vacuum tubes-and has involved complicated and expensive cabling;

Features and objects of the invention are the provision ol' circuital arrangements that'wll reduce materially the number of vacuum tubes required'anda'lso reduce cabling complexities and costs to a minimum. These features and objects in a general way are accomplished by making as many ofthe vacuum tubes andv necessary cablingcommon to as many of the energizing or writing,y coils of writing heads as is possible.

in the embodiment of the invention hereinafter shown and described in detail a single set of vacuum tubes` is utilized in a common circuit arrangement to supply the necessary write "0 energizing currents simultaneously from a common source of electricalvenergy'for all seven write 0 energizing coil sections of the energizing coils ofgseven writingheads ofaselectedchannel Common 2,787,514 Patented Apr. 2, 1957 cabling between this set of tubes and the said energizing coil sections reduces the cost of necessary tubes for elfectively energizing the coils of all seven heads seven'- fold. The energizing coil of each head also includes a write l coil section. Separate electron discharge means in the form of vacuum tubes and separate circuits are required to control independently the selective supply of write i energizing currents to each of the seven write l coil sections. The same source of electric energy, however, may be utilized for supplying both the write 0 and write l energizing currents forv the respective coil sections of all the write head c'oilsl Use of the! same source and of as much common cabling a's possible as will be presently described between the source and respective coil sections of the respective writing heads provide material savings in cabling costs and material reduction in cabling complexities. Therev may, of course, be more than or less than seven heads in a group. The savings are commensurate with the number of heads in a group.

In the circuital arrangement of this invention current pulses which are utilized to energize the respective write 0 and write l coil sections of the energizing coils of the individual writing heads are all derived from the common source of electric energy by the use of triode tubes in the associated circuits which become conducting in response to control signals from conventional and circuit means. Whenever the proper tubes become con ducting as instructed by said signals, the required energizing current iiows in the proper writing coil sections ofthe various heads.

Objects and features of the invention are to provide electrical circuits andy means for supplying write coil energizing currents of proper magnitude or intensity and direction from the common source to the write coil sections of the respective writing heads to cause any of them to write either "0 or l magnetically as instructed upon the magnetic surface and in which the number of vacuum tubes and circuit connections between them and the sections of write coils are reduced to a minimum.

Further objects and features of the invention are the provision of manufacturing economies asV a result both ofmaterial reduction in the necessary number of vacuum tubes and other component parts required in the circuit arrangement and of reduction in cabling time and in labor required to connect the various circuit components together.

Further objects and features of the invention are the provisio-n of a novel method of energizing a plurality of magnetic writing heads to cause any thereof to effect magnetic writing of either of two types of magnetic informationv by the use of electric energies of different magnitudes or intensities derived from a commonA electrical energy source.

Further objects and features of the invention are to provide a method of connecting a plurality of magnetic writing heads to a common electrical energy source and to supply electrical energies of two different kinds from said source to all of said heads as desired whereby when electrical energy of one kind is supplied to all the writing heads from the source all will tend` to write`r magnetic information of one type unless electric energiesl ofboth kinds are supplied from said source simultaneously and in opposition to each other to selected ofthe writing heads in which event those selected writing heads will instead write magnetic information of a second type rather than the first type.

Further objects and features of the invention arey to effect material savings in required parts and in cabling costsby the practice ofthe said methods.

Other" objects and features of the invention willbecome apparent from the following description and the accompanying drawing which is a wiring diagram of an electric circuit embodying the invention.

Referring to the drawing, a plurality, in this instance seven, write energizing coil sections 10 one for each of seven, independent magnetic writing heads are provided. The writing heads themselves being of conventional construction are not shown. A balancing resistor 11 is connected in series with each coil section 10. The use of the balancing resistors 11 is optional. All of the coil sections have the same number ci turns (50 in this embodiment) and the balancing resistors 11 each have the same magnitude (680 ohms in this embodiment). All seven of the coil sections 10 are connected to a common wire or line 12 leading to a common electrical energy source of positive potential at A, in this instance +270 volts. All seven of the balancing resistors 11 are connected to a common plate lead wire 13. The seven branch circuits I-VII, inclusive, each consisting of a write 0 coil section 10 and a balancing resistor 11 are thus in electrical parallel connection between said plus line 12 and said plate lead wire 13. Any current caused to flow from the plate lead wire 13 to the positive potential at A via line 12, as will be presently described, subdivides into the seven like branch circuits LVII, inclusive, so that currents i of equal magnitude ilow in each said branch circuit simultaneously. The current i in each branch circuit is a write 0 current for each. Since this current i ows simultaneously in the seven write 0 coil sections 10, the seven Writing heads with which said sections are independently associated all will write 0 simultaneously unless instructed differently.

In order to provide different writing instructions independently as desired for each of the seven writing heads, its write coil also includes a write "1 coil section 14. One write l coil section 14 is connected to each write 0 coil section 10. Thus, one write 0 coil section 10 and one write l coil section constitutes the Write coil for one of each of the seven writing heads. All the write l coil sections 14 have identical numbers of turns (50 in the present embodiment) and other electrical characteristics. The terminal of each write l coil section 14 which is connected to the corresponding write 0 coil section 10 of one of the seven branch circuits -VII, inclusive, is also thereby connected to the common line 12 leading to the common electrical energy source of positive potential at A. The other terminals of the write l coil sections 14 are connected to seven independent lead wires 15, 16, 17, 1S, 19, 20 and 21, respectively, so that a write l current of 2i magnitude may be caused to flow independently from any one or more of the seven independent lead wires to the positive potential at A, in this instance +270 volts, through any selected ones of the seven write l coil sections 14 in opposite direction to the write 0 z' current flowing in the respective write 0 coil sections 10 that are connected to such selected write l coil sections 14.

In order to provide for flow of a write 0 i current ow simultaneously in all the seven write "0 coil sections to the +270 volt potential at A, electron discharge means comprising a single triode vacuum tube V1 and a pair of twin triode vacuum tubes V2 and Va are provided. Vacuum tubes V2 and V3 are well known RMA 5687 type tubes and vacuum tube Vi is also a well known type being V2 of a 5687 type tube.

The four plates of the two twin triode tubes V2 and V3 are all connected to the common plate lead Wire 13. The four cathodes of the two twin triode tubes V2 and V3 are all connected to the common grounded Wire 22.

Four grid resistors 23 all of equal value and in this embodiment each having a value of 150 ohms are connected, respectively, to the four grids of the twin triode tubes V2 and V3. Each grid resistor 23 is also connected to the common grid lead wire 24. Thus, the two twin triodes V2 and V3 are in effect connected in multiple or electrical parallel and always operate in unison. The tubes V2 and Vs are normally maintained in non-conducting condition by appropriate bias on their grids as will be presently described. Conduction in said twin triode tubes V2 and V3 from their cathodes to their plates to provide said i current for each branch circuit I-VH, inclusive, simultaneously is controlled by the single control triode tube V1 as will now bc described.

The plate of tube V1 is connected at B to a source of positive electrical potential in this instance volts. The cathode of tube V1 is connected through the series connected resistors 25, 26 and 27 to a source of negative electrical potential at C, in this instance -60 volts. Resistor 25 in this embodiment has a value of 200 ohms. Each resistor 26 and 27, in this embodiment, has a value ot 1800 ohms. A single resistor having the total ohmic resistance of resistors 26 and 27 may replace them if desired.

The grid lead 24 from the tubes V2 and Vs is connected to the junction 28 between the resistors 25 and 26. This connection provides a negative bias from the -60 volt biasing source at C, via lead 24 through the four grid rcsistors 23 to lall four grids of thc twin triode tubes V2 and V3 and maintains them in a normally non-conducting condition unless control triode tube V1 is made conducting (ired) as will now be described.

A grid resistor 29 connects the grid of the triode Vi to the input junction 3? `of a conventional and circuit 31. This and circuit includes, for example, the germanium diode 32 connected to a selected channel lead wire 33 and, for example, the germanium diode 34 connected to a write signal lead wire 35. The junction 30 is connected through the in series resistors 36 and 3'7 at D to a source of positive electrical potential in this instance +l40 volt source. In the embodiment shown, resistors 36 and 37 have respectively the values of 15,000 ohms and 18,000 ohms. A single resistor having the total ohmic value of these two resistors may be substituted. With the and circuit arrangement shown, a cut oft bias is normally maintained on the grid of control tube Vi and it is non-conducting. Tube V1 only becomes conducting upon the simultaneous appearance of positive voltage pulses from the leads 33 and 35 ct the and circuit 31 at both diodes 32 and 34. Such simultaneous appearance blocks current flow through both diodes 32 and 34 to the +140 volt source at D. A plus pulse then appears at the junction .'50 which is transmitted through grid resistor 29 to the grid of tubc V1. This plus pulse tires control tube Vr. lt is suicient to render control tube Vi conducting, allowing current to ow from the +60 volt source at C through resistors 27, 26 and 2S, through the tube V1 to the +140 volt potential at B. This current flow in tube Vi changes the biasing potential at junction 28 because of the voltage drops across the resistors 26 and 27. As a result, thc bias on the four grids of the tubes V2 and Vs is changed and both tubes V2 and V3 become conducting, allowing current to ow from the four grounded cathodes of said two tribes through the said tribes to the plate lead 13, through all seven branch circuits l-VH, inclusive each consisting of a write 0 coil section 10 and a balancing resistor 11), to the positive potential ot' +270 volts at A Via the common connecting line 12. The current in plate lead 13 then has a 7i magnitude which is equally divided into a current of i magnitude tiowing in cach write "0 coil section 10 of each of the branch circuits I-VII, inclusive. The seven writing heads (not shown) with which the seven respective write "0 coil sections 10 are independently associated thus will each be provided smultaneously with a write "0 ux for writing a "0 spot on the magnetic surface as a result of the i current so appearing in each of the seven write 0 coil sections 10.

To provide a write "1 ux for any selected ones of the seven writing heads, the write l coil sections 14 lof ithose .writing-:heads which .are selected to write l ows `in any selected write "1.coil section 14, the ux therefrom kis in opposition-to the ilux caused by the i current simultaneously flowing in the write 0 coil sectionsassociated with suchselected write 1 coil .sec-

tions. This 2z' .current flux overcomes .the i .current 4ilux .and the selected write heads then write i" spots rather than "0 spots on the magnetic surface.

.While all the write .1 coil sections 1eare connected to the +270 volt .line .12.at their junctions with the write 0vcoil sections .10, the other terminal of each coil'section ..14 is connected .in an lindependent electrical circuit.

Electron .discharge means in this embodiment comprisinga singletwin triode tube V1 of the 5687 type hereinbefore Vdescribed ,is provided. This V 1 tube comprises the control tube section V4 and the 2i current providing section V5.

Lead from the Write 1 coil section i4 that `is connected at .one end to the write 0 coil 10 of branch cir- .cuit I is connected at the .otherend to the plate of the section V5. Grid resistor is connected to the grid of tube section Vs and .to a grid lead 51. This yresistor in the instant application has a value of 150 ohms.

The plate of .control tube section V4 is connected at E to a source of positive electrical potential, in this instance +140 volts. The cathode of tube section V4 is con nected through the in series resistors 52, 53, 54 to a source of negative electrical potential, in this instance 60 volts vat F. Resistors 52, 53 and 54E- in this instance have values, respectively, of 200 ohms, 1,800 ohms ,and 1,800 ohms. A single resistor having the total ohmic value of resistors 53 and 54 may be substituted therefor. The ,grid lead 51 from tube section V5 ,is connected to the junction 55 between the resistors 52 and 53.

A grid resistor 56 .which in this embodiment has a value of 150 ohms is connected to the grid of control tube section Vi and to the junction 57 of an and circuit 58. y,This and circuit 58 includes, for example, the germanium diode59 with its channel lead wire 60 and, for

example, the germanium diode 61 and lead wire 62.

.Preferably Athe channel lead wire is connected to the ysame selected channel pulse source as that connected to 'lead wire 33. Both diodes 59 and 61 are connected through the series connected resistors 63 and 64, in this instance, respectively, of 15,000 and 18,000 ohms to a source of positive electrical potential, in this instance +140 volts, -at G. A single resistor having the total ohmic value of resistors 63 and 64 may be substituted therefor. Lead wire 62 from diode 61 is connected to the junction point 65 of a second and circuit 66. This second and7 circuit 66 includes, for example, the germanium diode .67 with its lead wire 68, and asecond germanium diode 69 with its lead Wire 70.

Lead wire 68 comes from a signal source (not shown) `which must provide a plus voltage pulse at diode 67 .when a write l is to be eected by the write head bearing the write 1 coil .section 14 which is connected to .the write "0 coil section 10 of branch circuit i. Lead Wire 70 comes from a different instructing signal source (not shown) which must provide a plus voltage pulse at diode 69 simultaneously with the pulse appearing at diode .67 to activate the particular Write head of branch circuit I to write l rather than 0 as will be described more .in detail.

Diodes 67 and 69 and junction point 65 are connected bythe in seriesresistors 'ilfand 72 (in this instance of thesarne ohmic valuesfas resistors 36 and 37") to a source ,offlpositive electricaly potential, in this instance volts,

vat H. A single resistor whose total ohmic value-is that Aofresistors v71 and 752 may :be substituted therefor.

The cathode of tube section V5 is grounded.

With the vconnections .shown .both tube sections V4 and V5 of the Vr tube are normally .non-conducting because of the biasing voltages on their respective grids. Whenever control tube section V4 is fired by signals .to its and circuits 58 and 66 as will be described it .becorses conducting. This permits ilow of current from the +60 volt source at F through resistors 5d, 53 and 52, to the cathode of tube section V4 and through said tube section to the +140 potential at E. The grid bias of tube section V5 is thus changed because of the voltage drop across resistors 53 and 54 and tube section V5 becomes conducting. When tube section V5 becomes conducting a current 2i flows from the grounded cathode of tube section V 5, through said tube section, through lead wire 15, through the branch I connected write l coil section ifi to the positive potential of +270 volts at A via line l2. This 2i current flow is in opposite direction to the i current simultaneously llowing in the write 0 coil section l0 of branch circuit I and the flux from the said 2i current easily overcomes the ux of the said z' current and causes the particular write head with which the said two particular write 0 and write "1 coil sections 10 and 14 are associated to write a 1 rather than a "0 on the magnetic surface.

To fire or render control tube section V4 conducting, plus signal pulses must arrive simultaneously at all four diodes 59, 6l, 67 and 69 via the respective leads 60, 62, 68 and 70 of the twoy and circuits 58 and 66. Unless this condition is fulfilled control tube section V4 remains non-conducting and in consequence tube section V5 is also non-conducting and no 2z' current flows in the particular write l coil section 5.4 connected to lead 15.

The leads 1 6, i7, 18, i9, 20 and 21 connected to the respective other write "1 coil sections 15.. that are connected to the respective write 0 coil sections 10 of the other branch circuits il, Hi, IV, V, Vl and Vil are each connected independently with diiferent independent twin triode tubes identical with the twin triode Vr in the same way as lead 15 has been connected to the Vr tube. Each set of these other twin triodes is independently controlled by pairs of and circuits similar to the pairs of and circuits 58 and 66 so that a 2i current may be caused to llow independently in the same way in any selected one or more of said leads 16-21, inclusive, and consequently in the specific write l coil sections 14 connected to such selected leads and thus direct any selected write head to write a "1 spot rather than a 0 spot on the magnetic surface. As all the circuits and components thereof for providing 2i current in any selected of the leadsl6, 17, 18, 19, 20 and 2l are similar to the circuit and components for providing .2i current ow in lead 15, the circuit and components for providing 2z' current in lead 18 only is shown additionally in the drawings. Lead 13 provides for the 2z' current inthe write l coil section 14 that is in series with the write f0.coil section 10 of the branch .circuit 1V.

As can be seen from the drawings, in this embodiment a single twin triode tube Vrv of the '5687 type hereinbefore described is provided. This Viv tube which has an identical function as that of the Vr tube comprises the control tube section Vs and the 2i current providing section V7. Control tube section Ve is connected to and circuits to function in the saine way as control tube section Vi and tube section V7 is connected tolead i8 to function in the same Way with respect thereto as does tube section V5 with respect to lead 15.

For achieving this effect, lead 1S from the write l coil section 14 that is connected to the write 0 coil 10 of branch circuit IV is connected to the plate of tube section V7. The cathode of tube section Vv is grounded. Grid resistor $0 is connected to the grid of tube section Vv and to a grid lead Si. This resistor in the embodiment shown has a value of ohms.

The plate of control tube section 'Vs is connected at Y:maar 14 I to a source of positive electrical potential, in this instance +140 volts. The cathode of tube section Ve is connected through the in series resistors d2, 83 and 84 to a source of negative electrical potential, in this instance -60 volts, at M. Resistors S2, 83 and 34 have ohmic values identical, respectively, to those of resistors 52, 53 and 54. A single resistor having the total ohmic value of resistors 83 and S4 may be substituted therefor. The grid lead 81 from tube section V7 is connected to the junction 85 between the resistors 82 and 83.

The grid resistor 36 whose value is similar to that ct y grid resistor 56 is connected to the grid of control tube section Vs and to the junction 87 of an and circuit 8S. This and circuit 8S includes, for example, germanium diode 89 and its channel lead wire 9i) and also. for eX- ample, germanium diode 99 and its lead wire 922. Prell erably the channel lead wire 90 is connected to the same channel pulse source as channel lead wires 33 and ed. Both diodes 39 and 91 are connected through the series connected resistors 93 and 9a, res ectivelU of 15,000 and 18,000 ohms to source of positive electrical potential, in this instance +140 volts, at P. A single resistor having the total ohmic value of resistors 93 and may be substituted therefor. Lead wire 92 from diode 91 is connected to the junction point 95 of a second and circuit 96. The latter includes7 for example, a germanium diode 87 with its lead wire 92 and, for example, a second germanium diode 99 with its lead 100.

Lead wire 9S comes from a signal source (not shown) which must provide a plus voltage pulse at diode 97 when a write "1 is to be eiected by the Write head bearing the write "l coil section 14 which is connected to the write coil section 1@ of the branch circuit IV. Lead wire 190 comes from a different instructing signal source (not shown) which must provide a plus voltage pulse at diode 99 simultaneously with the plus voltage pulse appearing at diode 97 to activate the write head of branch circuit IV.

Diodes 97 and 99 and junction joint 9S are connected by the in series resistors 10i. and 1112, in this instance, respectively, of 15,000 and 18,000 ohms to a source of positive electrical potential, in this instance +140 volts, at R. A single resistor having the total ohmic value of these two resistors may replace them.

With the connections shown both tube sections V6 'i and V7 of the Vrv tube are normally non-conducting because of .the biasing voltages appearing on their respective grids and no 2z' current ordinarily `flows in lead 18 or in `the write l coil section 14 connected to said lead. When plus pulses appear simultaneously at all four diodes 89, 91, 97 and 99, control tube section V6 is fired and becomes conducting in the same way as control tube section V4. As a result tube section V7 similarly .to tube section V becomes conducting and a` current 2z' tlows from the grounded cathode of tube section V7, through said tube section, through lead wire 1S, through the branch IV connected write 1 coil section 14 to the positive potential of +270 volts at A via line 12. This 2z' current ow is in opposite direction to the i current flowing simultaneously in the write 0 i' coil section 10 of branch IV and the ux of said 2i current easily overcomes the flux of said last named z' current and causes the write head of branch circuit IV to write a l rather than a 0 on the magnetic surface. Unless control tube section V is lired or rendered conducting by simultaneous arrival of plus signal pulse at all four diodes 89, 91, 97 and 99 from the two and circuits 88 and 95, tube section V7 remains non-conducting and no 2i current ows in lead 18 or in the write 1 coil section 14 connected thereto.

With the circuital arrangements shown it is readily seen that the three tubes V1, V2 and V3 are common to all seven branch circuit write O coil sections and supply .the write 0 i' current simultaneously in all.

seven of these coil sections. Whenever these tubes V1,

V2 and V3 are activated as hereinabove described by signals from the and circuit 31, all seven write heads are energized and will write 0 as a result of said i current iiowing in each branch circuit LVII, inclusive, unless different instructions are received by the flow of reversely directed 2i current in any selected write l coil sections 14. Any of the said seven heads may instead be selected and instructed to write a l by effecting 2i current ow of reverse direction in the write 1 coil section 14 associated with such selected heads by independently activated separate tubes, i. g. tubes like tubes Vr or Viv as herein described. The 2i current owing in any such selected write 1 coil sections 14 overcomes the flux of the i current owing simultaneously in the write 0 coils 10 connected to such write l coil sections and heads activated simultaneously both by i and 2i current caused tiuxes, write 1 rather than 0 on the magnetic surface. The same common electrical energy source of positive potential of 270 volts at A is used to provide both the and 2i currents.

The arrangement described thus provides method and means for effecting a material saving in the overall number of tubes required over what would be necessary if separate sets of tubes were used for providing current independently for each write O coil section 10. Use of the same set of three tubes Vi, V2 and V3 is made possible by the connection of all the Write 0 coil sections 10 to the common line 12 `to the electrical energy source of positive potential at A and by the connection of all write 0 coil sections and their associated balancing resistors 11 to the plate lead 13. In other words, `the parallel connections of the seven branch circuits LVII, inclusive, each consisting of a write 0 coil section 10 and a balancing resistor 11 between the corninon plus line 12 and the common plate lead 13 permits use of the single tube set V1, V2 and V3 for providing i current for all write heads simultaneously. Since the tubes V1, V2 and V3 are used to provide .the i current for all seven bits of the channel, the cost per seven bit channel (because the V1 tube is 1/2 of a V2 or V3 tube) is 2.5/7 tubes instead of 17.5/7 which would be the cost it' separate sets of V1, V2 and V3 tubes were used for each of the seven branch circuits LVII, inclusive. Moreover, .the use of common plus line 12 and also the use of the common plate lead 13 to the V2 and V3 tubes results in material savings in the costs of cabling and also reduces labor time needed to connect the circuit components together for operation.

While a specific embodiment of the invention has been described herein, variations in detail, substitutions and changes in circuit elements and components thereof within the scope of the appended claims are possible and are contemplated. There is no intention of limitation therefore to the exact arrangements herein shown and described.

What is claimed is:

1. In combination with a plurality of magnetic writing heads each having coils, said heads serving to effect magnetic writing of a tirst type or a second type of magnetic information on a magnetic surface, electrical circuit means for simultaneously supplying electrical writing current energy of a iirst kind and magnitude to all of said coils from a common electrical source so that all writing heads whose coils are only supplied with this current energy will effect magnetic writing of the first type, separate electrical circuit means for supplying electrical writing current energy of a second kind and different magnitude from said source independently to any selected coils of said plurality of coils simultaneously with the supply thereto of said writing current energy of the first kind and in opposition thereto to oppose the effect of the latter in selected heads and with the said selected coils effect magnetic writing of the second type, and selecting means included in said separate electrical circuit means for determining the coils to be selected, whereby all heads supplied only with said Writing current .energy of the first kind will eect magneticvwriting of said first typeand those selected vcoils which are additionally .supplied with said writing current energy of ,the secondkind will effect magnetic writing of said second type.

2. In combination with a plurality of magnetic writing heads each having coils, said heads serving to effect magnetic writing of a first type or a second type of magnetic information on a magnetic. surface, circuit means including a common set of vacuum tubes for simultaneously supplying identicalelectric writing current energy ofk a first kind to all of such coils from a common source of electrical energy so that all writing heads whose coils are only supplied with saidcurrent energy will effect magnetic writing or" `the `first kind, separate circuit means eachv including separate vacuum tubes for supplying elec trical writing current energy of a second kind from said source independently to any of the said coils as may be selected simultaneously with the supply of electrical writin g current energy of the first kind to all of said coils and in opposition thereto and with the selected coils thus provide a net writing current energy that will effect magnetic writing of .a second kind, and selecting means included in said separate circuit means for determining the coils to be selected, whereby all coils supplied only with electrical writing current energy of the first kind will effect magnetic writing of a first kind, and those selected coils which are additionally supplied with electrical writing current energy of the second kind ywillinstead effect magnetic writing of a secondkind.

3. In combination with a group of magnetic writing vhead coils each consisting of a firstcoil section and a second coil section, sai-d coils. being adapted to effect magnetic writing of a first type of magnetic information or a second type of magnetic information on a magnetic surface as determined by the supply of electrical writing currents to the coil sections, a common electrical source, electrical circuit means for simultaneously supplying electrical writing current of a first kind and magnitude to all of the first sections of the coils from said source, and separate electrical circuit means connected independently to said source and to a different one of each said second coil sections for independently supplying each said second coil section as may be selected with electrical writing current of a second kind which is of different magnitude than said first named kind of current and in opposition thereto simultaneously with the supply of said first kind of current to all of said first coil sections, whereby all coils whose first sections only are supplied with said first kind of current will effect magnetic writing of said first type and those coils whose selected sectiond sections are additionally and simultaneously supplied with said current of the second kind will effect magnetic writing of said second type.

4. The invention of claim 3, including selecting means in the separate electric circuit means for selecting second coil sections which are to be supplied with said current of said second kind.

5. In apparatus of the character described a plurality of like magnetic writing head coils each comprising two coil sections, an electrical circuit commonly connected to one of the two sections of all of said coils, electron discharge means in said circuit to effect current flow of like intensity simultaneously in all of the commonly connected sections, means in said circuit for rendering said electron discharge means conductive to effect said current flow, electrical circuits one connected independently to each other section of each coil and separate electron discharge means in each of said last named electrical circuits to effect current flow in any selected ones of said other sections of said coils which is of different intensity from that flowing in their first named sections and in opposite direction thereto, and separate means in each of said last named electrical circuits for rendering the separate electron discharge means therein conductive to effect said last named current flow of different intensity inthe said other coil :sections-as ymay be selected.

6. Circuital arrangements for energizing write head coils of a group of magnetic writing heads to effect magnetic writing thereby on a magnetic surface of either of two types of magnetic information comprising a common source of electrical energy, a set of electron discharge devices, al1-electric circuit connecting said devices in com- ,mon to all of said coils and to said source, means for tive so that energizing current of a second determined magnitude flows through the said separate electric cir cuits connected to the conductors of said last named devices through selected coils to the said electrical energy source simultaneously with the flow in said last named coils of the first named current and in opposing relationship thereto, whereby all heads whose coils are supplied only with the first named current vwill write one of the two types of magnetic information and all heads whose coils additionally and simultaneously are supplied with the second named current will write the other of the two types of magnetic information.

7. ,in apparatus of the character described, a plurality of magnetic writing head coil sections connected in multiple, a common source .of electric energy connected to all the said sections, normally non-conductive vacuum tube means connected commonly to all said sections to provide fiow of current of like magnitude simultaneously in all said sections to said source whenever said vacuum tube means become conductive, means for firing said vacuum tube means to render it conductive, second writing head coil sections each connected to a different one of the first named writing head coil sections, a plurality of independent normally non-conductive vacuum tubes connected separately each to a different one of said second sections and to said common source, means for firing any selected of said last named vacuum tubes to render those selected conductive thereby providing iiow of current to said source through the second coil sections connected to the selected conductive vacuum tubes, said last named current having a diierent magnitude than that of said first named current and bein-g in opposition thereto.

8. in apparatus of the character described a source of electric energy, a plurality of branch circuits connected in parallel each including a writing head coil section, a common lead connecting all said branch circuits to said source, normally non-conductive triode tubes connected commonly to all said branch circuits and in conjunction with said source to provide flow of current of like inagnitude to said source simultaneously in all said branch circuits whenever said triode tubes become conductive, means firing said tubes to render them conductive, separate second writing head coil sections each serially connected to a different one of the first named coil sections, a plurality of separate normally non-conductive triode tubes each connected separately to a different one of said second writing head coil sections and in conjunction with said source to provide flow of current to said source of different magnitude and direction than said first named current independently in any selected second coil section whenever the particular ones of said last named triode tubes connected to said selected sections are rendered conductive, and means for selectively firing any of said last named triode tubes to render them conductive.

9. ln apparatus of the character described a source of electric energy, a plurality of branch circuits connected in parallel each including a writing head coil section, common cabling connecting all said branch circuits to said source, a pair of normally non-conductive twin triode tubes connected in multiple and commonly to all of said branch circuits and in conjunction with said source to provide ilow of current of like magnitude and direction to said source simultaneously in all said branch circuits whenever said pair of twin triode tubes becomes conductive, means including a single control triode tube interconnected with said pair of twin triode tubes to render them conductive, separate second writing head coil sections each serially connected to a different one of said rst named coil sections and also through said common cabling to said source, a plurality of separate normally non-Conductive triode tube sections each connected separately to a diierent one of said second writing head coil sections and in conjunction with said source to provide flow of current to said source of diterent magnitude and direction than said irst named current independently in any selected second coil section whenever the particular ones oi said last named triode tube sections connected to said selected second coil sections is rendered conductive, and separate circuit means each including a control triode tube section connected to a different one of said normally non-conductive triode tube sections for selectively tiring any of the latter to render them conductive.

in apparatus for writing magnetic information which is either a 0" or a l fragment of information, a group of coils each comprising a write O section and a write l section, a common lead connecting one terminal of ail the write 0 sections and one terminal of all the write l sections to a common source of positive electric potential, a second common lead connected to the iother terminals of all the write "0 sections, separate additional leads one connected respectively to a different one of each other terminal of the write "1 sections, a single set of normally non-conducting triode vacuum tubes connected to said second-named common lead, a tiring vacuum tube connected to said set of vacuum tubes, an "and circuit connection to said firing vacuum tube to re the latter and thereby render said set of triode tubes conducting to permit an i current to flow simultaneously through each write 0 coil section to the said source, a normally non-conducting triode tube connected independently to each dilerent one of said separate additional leads, a firing vacuum tube for each said last named triode tube, separate and circuit connections to each said last named ring tube to tire each independently as desired and thereby render that last named triode tube associated therewith conducting, any of said last named triode tubes being rendered conductive causing a 2i current to flow to said source through the write "1 coil section connected therewith simultaneously and in opposite direction to the i current flowing in the write "0 coil sections, whereby all coils in whose Write 0 sections current i only iiows will eiect magnetic writing of "0 information and those coils in whose respective sections current i" and current 2i ow simultaneously and oppositely will effect magnetic writing of 1 information.

References Cited in the file of this patent UNITED STATES PATENTS 2,633,402 Fleming Mar. 3l, 1953 2,679,551 Newby May 25, 1954 

